From Plato and Aristotle to Descartes, the great thinkers have for millennia argued over what is known in philosophy as the “mind-body problem,” the relationship between spirit and flesh. Dualism tends to win the day: The mind and the body, while linked, are separate. They exist independently, perhaps mingling but not merging.

The debate lives on these days in less abstract form in the United States: How much of a difference should it make to health care — and health insurance — if a condition is physical or mental?

Decades of culture change and recent scientific studies have blurred the line between these types of disorders. Now a critical moment has been reached in a 15-year debate in statehouses and in Congress over whether treatment for problems like depression, addiction and schizophrenia should get the same coverage by insurance companies as, say, diabetes, heart disease and cancer.

This month, the House passed a bill that would require insurance companies to provide mental health insurance parity. It was the first time it has approved a proposal so substantial.

The bill would ban insurance companies from setting lower limits on treatment for mental health problems than on treatment for physical problems, including doctor visits and hospital stays. It would also disallow higher co-payments. The insurance industry is up in arms, as are others who envision sharply higher premiums and a free-for-all over claims for coverage of things like jet lag and caffeine addiction.